hawc andrew smith - university of maryland tev astrophysics ii, august 28,2006 high altitude water...

Andrew Smith - University of MarylandTeV Astrophysics II, August 28,2006

HAWC

High Altitude Water Cherenkov experiment

HAWC

Andrew Smith, University of Maryland


HAWC

Detector Layout

Milagro:450 PMT (25x18) shallow (1.4m) layer273 PMT (19x13) deep (5.5m) layer175 PMT outriggers

Instrumented Area: ~40,000m2

PMT spacing: 2.8mShallow Area: 3500m2

Deep Area: 2200m2

HAWC:900 PMTs (30x30)5.0m spacingSingle layer with 4m depth

Instrumented Area: 22,500m2

PMT spacing: 5.0mShallow Area: 22,500m2

Deep Area: 22,500m2

HAWCMilagro


HAWC

Detector Layout

Milagro: 2 layers at depths1.4m – “Air Shower” Layer5.5m – “Muon” Layer

HAWC: Single intermediate layerOpaque curtains between cells

4m

5.5

m

5 m

2.8 m

1.4

m


HAWC

Curtains• HAWC single muon rate = ~1MHz • Install curtains to optically isolate the PMTs.

• Intrinsic Gamma hadron separation


HAWC

4300m

2600m

Difference between 2600m (Milagro) and 4300m:~ 6x number of particles~ 2-3x lower energy threshold

Altitude


HAWC

Milagro Instrumentation• 900 8” Hamamatsu PMTs

– Bases, encapsulation• Single rg59 cable for data and

HV.• Custom front end boards

– Signal shaping and threshold detection– Trigger primitive generation– Pulse height through TOT method.

• FastBus TDC’s– Capable of ~2000Hz or 6MB/s readout

• VME-FastBus interface for readout


HAWC

Gamma/Hadron Separation

Lateral distribution of EM energy and muons.

Part

icle

Den

sit

y (

Arb

itra

ry U

nit

s)


HAWC

Triggering with Curtains• Multiplicity trigger at ~80 PMTs gives same trigger rate as Milagro at 50 PMTs• Much higher Gamma area.

Milagro

HAWC

Gamma-Ray Rate


HAWC

= ~0.4 deg = ~0.25 deg

Angular Resolution

nTrigger = 50 PMTs nTrigger = 200 PMTs


HAWC

Gamma/Hadron Separation

Gam

mas

Pro

ton

s30 GeV 70 GeV 230 GeV

20 GeV 70 GeV 270 GeVSize of HAWC

Size of Milagro deep layer Energy Distribution at ground level


HAWC

Gamma/Hadron Separation“Compactness”

• Use new /hadron discrimination variable for HAW that excludes the core location.

CMilagro = (nPMTs > 2 PE) (Max “muon layer” hit)

CHAWC = (nPMTs > 2 PE) (Max “muon layer” hit >30m from core)


HAWC

/ hadron Separation

Cut: nTop/cxPE>5.0Eff = 34%Eff CR= 3%

Cut: nTop/cxPE>5.0Eff = 56%Eff CR= 1.5%

Q Factor (sig/√bg)

Cuts soft hard

HAWC 2.0 4.5

HESS 3.2 4.4

= 56% -> 28%

CR= 3% -> 0.4%

(shape only)

HESS


HAWC

Effective AreaGamma Area: <30o nTop/cxPE>5.0 <1.0O

200 PMT Trigger80 PMT Trigger20 PMT Trigger

Area ofGLAST

Detector Size


HAWC

Energy (Crab Spectrum, nTop/cxPE>5.0., <30O)Significance from

Crab Transit (~5 hr) 4

Crab signif/year ~80

5 point source

sensitivity reach ~60mCrabof 1 year survey

Energy Resolution ~30% above median

Angular Resolution 0.25O-0.40O

S/B (hard cuts) ~ 1:1 for CrabTypical day 20 excess on 25 bkg

Q (sig/√bg) ( miniHAWC/Milagro) = 15

HAWC Sensitivity


HAWC

Sensitivity Increase (Q factor)

• 15x Sensitivity increase over Milagro~3x from Altitude, Area~3x from /hadron separation~1.5x from Angular resolution

• ~60mCrab sensitivity (5 in 1year)


HAWC

GRB Sensitivity

Fluence Sensitivity to 100s GRB.

Both Milagro and HAWC can “self trigger” and generate alerts in real time.

GRB rate in FOV ~100 GRB/year (BATSE rate)

MilagroHAWC


HAWC

The Diffuse Galactic Plane

Use Neutral H map to trace out VHE Gamma-Ray flux. Normalize to Milagro observed TeV diffuse emission from the Galactic plane.

HAWC Diffuse Galaxy in 1 year

Galactic Neutral Hydrogen


HAWC

Pond Design• Fiducial volume: 150m x 150m x 4m• Actual size: 170m x 170m x 5m• 1:1 slope at perimeter• 4½m depth to allow for 4m over PMTs.• Total volume: 115 Ml

170m

150m

4.5-5.0 m 6m


HAWC

Building Construction

• Prefabricated steel building– Components manufactured

at factory.– Shipped to site (~9 trucks)– Beams bolted not welded.– Cost ~1.5M$ (not installed)

• Building installation ~400 k$• Pond excavation ~300 k$• Liner cost ~600 k$

Total facility cost ~3.0-3.5M$ 170m 170m


HAWC

Sierra Negra, Mexico

~1 ½ hr drive from Puebla

~4hr drive from Mexico City

Saddle between Sierra Negra (z=4500m) and Orizaba (z=5600m)

Site under development as a multiuse scientific facility.


HAWC


Water available from wells in valley and may be available at the site.


HAWC


Elevation = 4030mLatitude = 19O 00’NLongitude = 97O 17’ W

LMT – 50m dish


HAWC

YBJ Laboratory – Tibet, China

Elevation: 4300mLatitude: 30O 13’ NLongitude: 90O 28’ E

Lots of space.Available power.Available water.

Tibet Air Shower Array


HAWC

Geomagnetic Cutoff

Milagro:3.5 GV

Tibet- 13.1 GVLa Paz: 12.0 GV

Sierra Negra: 7.7 GV

Singles rates at sites under consideration are reduced by ~20-30% due to improved geomagnetic cutoff.


HAWC

Triggering and DAQ

• Milagro DAQ in its current form should be capable of triggering to multiplicities as low as ~80 PMTs. (~1800 Hz)

• Simulation indicates that we can reconstruct gamma-ray events as small as ~20 PMTs.

• Potentially huge sensitivity increase to GRBs if DAQ can be easily upgraded.


HAWC

DAQ Upgrade• Move to VME TDC bases

DAQ.• CAEN 1190• Capable of >40MB/s • 10-20kHz Readout.• Cost ~100k$


HAWC

Costs• Facility ~$3.5M

– Excavation, Liner, Building, Roads etc.

• Water Recirculation System ~$100k• Cabling DAQ Upgrade ~$200k• Other costs: ~$600k

– Computing, Archiving, Monitoring, Cooling, Shipping…

• Getting the Water (site dependent)• Electrical (site dependent)• Communications (site dependent)

Price ~$200/m2


HAWC

Detector Sensitivity (Single Location)

HAWCHAWC II

GLAST

EGRET

Crab Nebula

WhippleVERITAS/HESS

Current synoptic instruments


HAWC

Conclusion• Surface arrays complement IACTs

– Variable Sources– Diffuse Sources– GLAST/IceCube Coincidence– High Energy

• Sensitivity computations don’t include weighting techniques used by Milagro.– Expect >~x2 sensitivity increase (or more).

• Harder spectra favor high energy instruments.– For an =-2.0 source that extends to >~10TeV 30 mCrab HESS(180GeV) source = 300 mCrab Milagro(10 TeV w/Weighted Analysis)

– Milagro would detect hard HESS GP sources if it was in the Southern Hemisphere.

– HAWC sensitivity is an order of magnitude lower.

hawc andrew smith - university of maryland tev astrophysics ii, august 28,2006 high altitude water...

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